This invention relates to exhaust mufflers, and more particularly to the provision of a sound deadening means useful to reduce impulse and exhaust noise of a cyclically operating pneumatic device. Being of simple, lightweight construction, the muffler means is well adapted to be advantageously embodied in numerous different air-operated machines or hand tools for performing a variety of work. By way of example only, the invention is herein shown and described as applied to a riveting tool of the pneumo-hydraulic type disclosed in U.S. Pat. No. 3,254,522 to Elliott et al., but it will be understood usage of the invention is not thus limited.
According to one method of reducing sound level as heretofore practiced a flow restricting means is provided in an exhaust passage. Unfortunately the resulting lower sound level is then attained at the expense of a longer time of exhaust flow and hence slower operation of the pneumatic device before its work cycle can be repeated.